The controversial sprinter Justin Gatlin does not understand why people insist on calling him a two-times drugs cheat and want him kicked out of athletics.

The American, who has served two doping bans, also expects future generations to look at him in a less judgmental fashion, he said, prior to the US world championships trials where he will run only the 200m.

“Last time I checked, someone who takes medication for a disorder is not a doper,” said Gatlin of his first drugs violation when he tested positive in 2001 for an amphetamine contained in attention deficit disorder medication (ADD) he had taken since a youth. “Other people in the sport have taken the same medication I had for ADD and only got warnings,” he added of the two-year ban that was later reduced to one. “I didn’t.”

Talk of that suspension might eventually have faded or been downplayed until the 2004 Olympic gold medallist and 2005 world champion failed a test for the banned steroid testosterone in 2006. He was banned for four years, though many thought that would be the end of his career. To the ire of many he has become even better since becoming eligible to run again in 2010.

No one has beaten him at either 100m or 200m since 2013, while this year, aged 33, he has set or equalled lifetime bests in both and become a serious threat to dethrone Usain Bolt at August’s world championships in Beijing.

“If I felt like I did anything that I was trying to take away from the sport of track and field, then I would stand up and say ‘yes, I am guilty and I did this. Please have mercy on me’,” Gatlin said.

He has never admitted to doping and continued to insist his 2006 test came from a massage therapist rubbing testosterone cream on to his legs, a contention the therapist has denied. “I have stuck to my story so far, and I have been honest with that,” Gatlin said. His four years off have given his legs new shelf life, he claimed. “I feel like 26 or 27 years old,” he said.

With Bolt having difficulty regaining his top form, many expect Gatlin to defeat the Jamaican in the 100m at the world championships, though the American will not go that far.

“I think that I am a serious threat to anybody out there who is trying to get that medal,” he said. “But I think those guys are a threat as well.”

He and Bolt have not raced since 2013 and, despite the Jamaican’s lack of form this year, Gatlin thinks his rival will be ready by August. “He’s done that in 2012,” Gatlin said. “He was beaten by his own team-mate at Olympic trials, in the 100m and 200m, and he seemed like he was going to lose the Olympics in 2012. But he woke up in the semi-finals and pulled it off.”

The pair will meet again in August and Gatlin is relishing the challenge in Beijing where he wants to take Bolt’s mantle as the world’s top sprinter. “I want it all again,” he said. “I want to be able to run the table. I want to be able to say that I have all those things once again.“

Athletics fans have been keen on the pair meeting before Beijing and while Gatlin accepts it would have been a tempting showdown, he was more interested in facing the Jamaican in China, when he expects him to be back at his best.

“What is it really going to amount to if I go out there and run against Usain when he is not at his best?,” Gatlin added. “That is not a great storyline. It is not a race I would like to go out and win. “I want Usain at his best, and I think he wants me at my best. That’s what people want to see.”